Broadnose sevengill shark
Broadnose sevengill shark | |
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Broadnose sevengill shark at Aquarium of the Bay | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Subdivision: | Selachimorpha |
Order: | Hexanchiformes |
Family: | Hexanchidae |
Genus: | Notorynchus |
Species: | N. cepedianus
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Binomial name | |
Notorynchus cepedianus (Péron, 1807)
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Range of the broadnose sevengill shark | |
Synonyms | |
Heptranchias haswelli* Ogilby, 1897
* ambiguous synonym |
The broadnose sevengill shark (Notorynchus cepedianus) is the only extant member of the genus Notorynchus, in the family
It is also known as sevengill shark or simply sevengill and was formerly known as cow shark and mud shark; it is called sevengill due to its seven gill slits. Because of this, it was listed along with the
Taxonomy
Name
The genus name Notorynchus a portmanteau is derived from the Ancient Greek νῶτον (nôton, meaning "back") prefixed to the Ancient Greek ῥῠ́γχος (rhúnkhos, meaning "snout").[6] It has been interpreted that this refers to the spots on the broadnose sevengill's dorsal. The specific epithet cepedianus is derived from a variation of the name Lacepede, which refers to Bernard Germain de Lacépède, a French naturalist during the late 18th and early 19th century.[7] Altogether, the scientific name as a whole literally means "Lacepede's back snout".
The common name "broadnose sevengill shark" refers to the seven gill slits the species possesses and the shape of its snout. Sometimes, the name is shortened to "sevengill shark" or simply "sevengill". However, a variety of other common names are known in many languages. Other known common names in English include the bluntnose sevengill shark, broad-snout, cowshark, ground shark, seven-gill cowshark, seven-gilled shark, spotted cow shark, spotted seven-gill shark, and Tasmanian tiger shark. Common names from other languages include cação-bruxa (Portuguese), cañabota gata, gatita, tiburón de 7 gallas, tiburón pinto, and tollo fume (Spanish), ebisuzame and minami-ebisuzame (Japanese), gevlekte zevenkieuwshaai (Dutch), Kammzähner and Siebenkiemiger Pazifischer Kammzähner (German), koeihaai (Afrikaans), k'wet'thenéchte (Salish), platneus-sewekiefhaai (Afrikaans), platnez and requin malais (French), siedmioszpar plamisty (Polish), and tuatini (Maori).[3][5]
Description
The length at birth is 40–45 cm (15.5–17.5 in) while the mature male length is 1.5 m (4.9 ft) and mature female length is around 2.2 m (7.2 ft).[1] The maximum length found is 3.3 metres (11 ft).[8] The maximum recorded weight is 182 kg (401 lb) for a 2.91-metre (9.5 ft) individual.[9] The shark is large and active and has a large head but small eyes and snout.[5] The mouth is broad and prominent.[10] The shark has one dorsal fin at the back of the body that spans from the insertion to the tops of the pelvic fins.[5] The mottled grey and white body is covered in a variable number of small black spots.[10]
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Front part including the seven gills
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Bottom part
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Jaws
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Upper teeth
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Lower teeth
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CT scan of the broadnose sevengill shark's braincase
Range and habitat
The broadnose sevengill has so far been found in the western Pacific Ocean off
Behavior
An opportunistic predator, the broadnose sevengill preys on a great variety of animals, and has been found at depths of 1,870 feet (570 meters), in offshore waters.
It can be one of the most abundant predators in coastal waters in summer; for example, in southeastern Tasmania, there is a high abundance of elasmobranches (including the gummy shark) in coastal regions in summer. In New Zealand, it is also one of the most common inshore sharks.[21] While it is mainly a nocturnal forager, it may opportunistically feed on prey casually found during the day; however, research in 2010 noted even amounts of activity during day and night. During this research, the shark was consistently detected at many depths, from bottom to near the surface, although it was mainly near the seafloor during the day. It also found that, as Norfolk Bay does not have adequate shelter cover, this species may use group formation to avoid predation.[13]
The sevengill, like all other members of
In 2004 and 2005, along with research for the
Research in 2014 also found that for the first time, reproductive hormones levels were found in the broadnose sevengill shark.[28] for a few years before venturing out. The probable predators of this species are larger sharks. Research from 2002 showed that although juvenile sevengill sharks utilize nursery areas in a similar way, males mature faster than females even if they are the same size and thus males are more likely to leave the nursery area before females.[29]
In 2004, John G Maisey of the American Museum of Natural History published a detailed analysis of the broadnose sevengill shark including imagery such as CT scans and morphology of its braincase.[30]
Conservation and relationship to humans
The broadnose sevengill is listed by the IUCN Red List as Vulnerable throughout its range. [5] This species likely suffers great ongoing pressure[1] from various types of fisheries, and from frequently being caught as bycatch. In Argentina, it's fished by rod and reel and broadnose sevengill shark fishing competitions have been occurring since the 1960s.[27] It is also threatened by water pollution and is hunted for its liveroil and hide which is considered good quality in places such as China. In the early 1980s, intense fishing in the San Francisco Bay caused a local decline. In June 2018 the New Zealand Department of Conservation classified the broadnose sevengill shark as "Not Threatened" with the qualifiers "Data Poor" and "Secure Overseas" under the New Zealand Threat Classification System.[31]
Its meat and fins are in demand in countries such as the US, Brazil, Spain, Germany, Netherlands and Israel, and is packaged for frozen food.[32] The broadnose sevengill is also a source of vitamin A and utilized by South African sport anglers for winter tournaments, however, this shark is not easy to land despite being readily hooked.[4]
It is frequently seen by tourists[33] and in temperate water aquariums and can adapt to captivity.[34] One of the aquariums that houses the broadnose sevengill shark, Oregon Coast Aquarium in Newport, Oregon, has featured it as a "keynote species".[35] There is also an app Sevengill Shark Tracking "Shark Observers" that allows divers to log sightings that are added to the Shark Observation Network, where the information supports "environmental awareness, assessment and policy making, and public participation at a global level".[36]
Not many conservation measures are known but it has been recorded from one marine reserve in South Africa and it occurs in
The International Shark Attack File considers this shark to be potentially dangerous because of its proximity to humans, and because of its aggressive behavior when provoked. It has also been noted as being aggressive towards divers and spearfishermen in both public aquariums and the wild. In 2013, in Fiordland, New Zealand, a sevengill bit a diver's regulator and then her head.[5][39] Human remains were also supposedly found in one specimen's stomach. Seven attacks on humans by the broadnose sevengill have been recorded since the 16th century, with no known fatalities [citation needed]. In 2020 a 13 year old girl was bitten while surfing at Oreti Beach in New Zealand. The girl continued to surf for an hour before realizing her leg was bleeding.[40]
References
- ^ . Retrieved 19 November 2021.
- ISBN 978-0345547118.
- ^ ISBN 978-0195392944.
- ^ ISBN 1868253945.
- ^ a b c d e f g h "Sevengill shark". flmnh.ufl.edu. Archived from the original on December 15, 2012. Retrieved June 19, 2015.
- ^ Hart, J. L. (1973). Pacific Fishes of Canada (PDF). Fisheries Research Board of Canada. p. 28.
- ISBN 9780520222656.
- ^ "The Pelagic Shark Research Foundation - The Sharks of the Monterey Bay - Benthic Sharks". www.pelagic.org. Retrieved 2023-11-17.
- ISBN 978-0-19-539294-4.
- ^ OCLC 70133147.
- ^ "Fascinating Facts About Sevengill Sharks". kqed.org. August 2, 2013. Retrieved June 23, 2015.
- ISBN 9780691120720
- ^ PMID 21151925.
- hdl:11336/30393. Retrieved June 22, 2015.
- ISBN 9251042993.
- ISBN 1919713034.
- ISBN 978-1607029601.
- .
- ^ "Broadnose sevengill shark". montereybayaquarium.org. Retrieved June 22, 2015.
- ^ Qukula, Qama (5 February 2019). "Shark-eating killer whales lurking in Cape Town's waters". capetalk.co.za.
- ^ "Summer Series 6: Broadnose Sevengill Shark". National Institute of Water and Atmospheric Research. January 31, 2012. Retrieved June 22, 2015.
- ^ a b "Bottomfish – Broadnose sevengill shark". wdfw.wa.gov. Archived from the original on June 23, 2015. Retrieved June 22, 2015.
- ISBN 2831707005.
- ISBN 978-1421413105.
- ^ "Grey Nurse Shark Research". waza.org. Archived from the original on June 24, 2015. Retrieved June 23, 2015.
- ^ Braccini, J. M.; Troynikov, V. S.; Walker, T. I.; Mollet, H. F.; Ebert, D. A.; Barnett, A.; Kirby, N. (2010). "Incorporating heterogeneity into growth analyses of wild and captive broadnose sevengill sharks Notorynchus cepedianus". Moss Landing Marine Laboratories/California State University. Retrieved June 22, 2015.
- ^ hdl:11336/103416.
- PMID 27293634.
- ^ "Long-term trends in catch composition from elasmobranch derbies in Elkhorn Slough, California". Marine Fisheries Review. January 1, 2007. Retrieved June 19, 2015.
- ^ Maisey, John G. (February 27, 2004). "Morphology of the Braincase in the Broadnose Sevengill Shark Notorynchus (Elasmobranchii, Hexanchiformes), Based on CT Scanning" (PDF). American Museum of Natural History. Retrieved August 9, 2015.
- OCLC 1042901090.
- ISBN 9251043612.
- ISBN 978-1135012618.
- ISBN 1577855388.
- ^ "Swimming with sharks: 'You're going to be in their space'". kval.com. March 31, 2012. Archived from the original on June 18, 2015. Retrieved June 18, 2015.
- ^ "Shark Observation Network". scientificamerican.com. Retrieved June 23, 2015.
- ^ "Sharks Attracting Attention In San Diego Waters". kpbs.org. June 4, 2013. Retrieved June 22, 2015.
- ^ "Shark". depi.vic.gov.au. Archived from the original on June 26, 2015. Retrieved June 23, 2015.
- ^ Turner, Anna (January 19, 2013). "Shark Attacks Diver in Fiordland". stuff.co.nz. Retrieved 21 Apr 2020.
- ^ Rowe, Damian (January 17, 2020). "Girl continues to surf after possible shark bite at Oreti Beach". stuff.co.nz. Retrieved 21 Apr 2020.